Drafting instrument



Dec. 25, 1951 3 PREMO DRAFTING INSTRUMENT Filed Sept. 9, 1946 H 0 WW 0 Wm M Z w a 7 W V M g W m 0 "W v m 6 m m k w w m HM m m a, W W K 4 v @HGW p miiiiii iiifiviiwvg ww wvwfw a?vim???f???wiamiifiv1???Him Patented Dec. 25,1951

UNITED STATES PATENT OFFICE 1 Claim.

This invention relates to drafting instruments.

One object of the invention is to provide a drafting instrument of polygonal outline having two of its edges at right angles and its hypotenuse divided into a plurality of straight portions making different angles with the base and altitude, so as to provide a large number of angles in a given instrument and reduce the need for using a protractor.

Another object is to provide a polygonal drafting instrument to replace the ordinary draftmans triangles with a single instrument capable of performing all the functions of several separate triangles.

Another object is to provide a polygonal drafting instrument having multiple dimension scales along its base and altitude with the divisions thereof indicated by needle point holes to facilitate quick and accurate layout of dimensions, the scales including, for example, graduations in ixteenths, tenths and twelfths of an inch, thereby including all graduations commonly used by draftsmen in the majority of their work.

Another object is to provide a polygonal drafting instrument having protractor graduations along the hypotenuse, with needle point holes indicating the angle in degrees struck off from a central point.

Another object is to provide a polygonal drafting instrument having an internally located small protractor on the opposite side of the center point from the large protractor, asset forth in the object immediately preceding, with the major graduations of the small protractor likewise indicated by needle point holes.

Another object is to provide a polygonal drafting instrument having a plurality of cut-out portions of outline suitable for forming lettering guides, in conjunction with dimension holes for indicating the heights of the letters to be drawn, and needle point holes for accurately locating these out out portions.

Another object is to provide a polygonal drafting instrument having a multiplicity of adjacently arranged hexagonal and circular cut-out portions, the circles being of a size inscribed in the corresponding hexagon, with needle point holes to indicate the corners of the square which is of the same cross dimension as the diameter of the circle, and preferably also with needle point holes to indicate the positions of the perpendicular cross-diameters so as to facilitate locating the centers of the circles, thereby facilitating the layout of bolts, screws, screw threads and the like. Anotherobject is to..provide a polygonal drafting instrument having rectilinear cutout portions with their sides arranged at varying angles to one another for the drawing of different machine details having lines arranged at such angles, for example, screw threads, worm threads, rack teeth, V-blocks and grooves, drill points, gibs, lathe centers, etc.

Another object is toprovide a polygonal drafting instrument having an elongated irregular curve cutout portion located between the cutout portions set forth in the preceding objects to facilitate the drawing of irregular curves which are not easily constructed by means of a compass.

Other objects and advantages of the invention will become apparent during the course of the following description of the accompanying drawing which shows a preferred embodiment of a polygonal drafting instrument according to the present invention, the figure being divided into two parts to accommodate it full-size upon a single sheet.

Referring to the drawing in detail, the two bracketed portions of the single figure show a polygonal drafting instrument, generally designated Ill. The figure is divided into two portions so as to show it in its full size, with the inch scales along its base and altitude in their exact dimensions, the ofiicially prescribed space on the drawing sheet being insufficient for showing the instrument full size in a single figure. The figure is also shown in its full size because of the extremely minute size of the needle point holes therein which would otherwise be obscured byreducing the size of the instrument in order to accommodate it within a single figure.

Angular edge portions provided with a base edge I I and altitude edge [2 at right angles to one another, and with an oblique or inclined edge 13 for convenience called the hypotenuse edge I3. The hypotenuse edge, however, is not a single straight line, as in a right triangle, but instead consists of three hypotenuse edge portion |4, l5 and 16 respectively. "Ihehypotenuse edge portions l4, l5 and 16 are so arranged that they form angles of 75 degrees, degrees and 45 degrees with the base edge l0, and their lengths are approximatelyequal so as to providethe maxi; mumbearing surface againstaT-square against which ,theyiare placed during use... ,Thus, theehyer 3 potenuse edge 13 i divided into approximately three equal portions at difierent angles to the base edge I I and altitude edge l2.

Edge scales The rectangular zone adjacent the base edge II is inscribed with scales ll, l8 and IS in three parallel rows graduated in sixteenths, tenths and twelfths of an inch, to the full length of six inche from the corner 28. Similarly, the rec- 28. The sides 4| and 42 are arranged at an angle of 60 degrees to the horizontal line 28, which in is cutout 38 is rectangular and is provided with tangular zone'adjacent the altitude edge 12 is H inscribed with scales 2!, 22 and 23 graduated in similar dimensions and extending to the full height of twelve inches to the apex or upper corner 24. The hypotenuse edge l3 extends from the upper corner 24 to a lower corner 2, as previously stated, in three substantially equal but differently angle-d edge portions. The graduations in the scales ll, I8, l9, 2|, 22 and 23 are indicated by lines terminating in needle point holes 26, these being staggered to accommodate them more easily and to place similar graduations at similar intervals along the same horizontal or vertical lines. The needle point holes 26 of the inner scales l8, I9, 22 and 23 are alternately interconnected by zigzag lines to facilitate locating the proper dimensions. As shown, each inch in the tenth inch scale l8 or 22 actually is divided into twentieths, whereaseach inch in the twelfth inch scale 19 or 23 is actually divided in twenty- 20 between the base and altitude edges H and l2, the inch graduations are indicated by the appropriate numerals.

Protra'ctor scales The hypotenuse edge [3 is graduated to form a protractor scale 21 extending between the reference lines 28 and29 parallel to the base and altitude-edges H and I2 respectively and intersecting at the-center point 30. The degree graduations in the protractor scale 21 are similarly indicated by staggered needle point holes 3| in parallel-rows, and are designated by the appropriate numerals-at degree intervals between theouter endsof the lines 28 and 29. The instrument is also provided with a minor protractor 32 adjacent the corner with lines extending thither from the central point at five degree intervals and terminating in needle point .holes "33, likewise in staggered arrangement in two rows. The point 30:also has a needle point "hole.

. Lettering guide portion The lettering guide portion, generally designated 34, islocatedin the lower left-hand-corner of the instrument immediately inside 'the zones containing the scales ll, [8, I 9, 2i, 22 and 23. The lettering guide portion 34 includes four rectilinear cutouts 35, 36, 3! and 38 andtwo sets of pencil holes 39 and '40. The cutouts '35 and36 aresimilar in outline but face oppositely and consist-ofinclined sides 4i and 42 subtending an'includedangle of 120 and having a needlepointlocating'hole 43 adjacent the vertex thereof. 0pp'osite the sides 4| and 42 is a vertical side 44-and at top and bottom are-horizontalsides 45 and-46 respectively, the latter coinciding with the line horizontal sides 52 and vertical sides 53 respectively. parallel to the base edge II and altitude edge 12 of the instrument. The pencil holes 39 and 40 are in staggered rows with the holes in each row A; inch and 1% inch apart respectively, giving increments of 1% inch and /20 inch respectively for ruling off letter heights. One of these holes in each of the groups 39 and 40 is on a horizontal line which bisects the angle between the sides 4| and 42, hence passes through the needle hole 43 so that measurements of letter height can be made equidistant from the center of this angle. The pencil holes 39 and; 40 are preferably tapered so as to facilitate insertion of a pencil point, the holes being of any convenient size, a satisfactory size having been 7 found, for example, to be approximately 2 of an inch diameter at-thebottom'andse inch at; the top.

' Thr'ead 'g'uz'de portion The thread guide portion generally designated 54 of the instrument is located immediately above the lettering guide portion 34 and consists of four rectilinear cutouts 5,5, 56, 51 and 58 respectively of different shapes and angles of sides. The :lowest cutout 55 has upper and lower sides 59 and 60 respectively inclined at angles of 30 to the base edge II, and including anglesof 60 and 120 respectively. The cutout '56 has upper and lower sides Bi and 62 inclined at angle of'45 to the base edge H,,hence including angles of 90. The cutout 51 has upper and lower sides 63 and 64' respectively inclined at angles of 41 to the base sedge ll, thereby subtending angles of 82 horizontally and 98 degrees vertically; The cutout 58'has upper and lower sides 65 and '66 respectively which are'inclined at an angle of to the base edge ll, thereby givingincluded angles of 29 horizontally and 151 vertically. The sides of the cutout'58 are truncated so that the in clined sides 65 and '66 'do'not meet but aref'joined by vertical sides 61. I

Above the cutout "58, is a triangular cutout G8 in the shape of a45-"90 right triangle, With'base 69 parallel to the base edge'll, its altitudeiflfl parallel to altitude edge [2, and with itsjhypoh enuse H at a 45 angle to'both. lThis triangular cutout 68 provides for the drawing, of lines with a"45 included angle'either horizontally or vertically. Each of the foregoing cutouts .55, 56, '5'! and 58 is provided with"needle pointhol'es 1.2 aligned with all or .certain of their corners, to facilitate locating 'the' cutout properly on the work. V

'To the right or thethread guide; portion i54'is an irregular curve cutout 73 of greatly elongated shape. This cutout has variably curved opposite sides T4 and interconnected by 'upper'and lower curved ends 16 and 1! respectively, andi's pass.

"Bolt and screw, guz'de portion *Ar-rarrgedtin an oblique1y-extending:zone1adi tion 18.

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jacent the hypotenuse edge l3 of the drafting instrument I is the bolt and screw guide por- This consists of two rows of cutouts 19 and 80 of graduated sizes according to the sizes of the heads of :bolts and screws to be drawn. The cutouts 19 include hexagons 8| with circumscribed squares 82 of the same cross-diameters and their corresponding cutouts 80 are circles likewise of the same cross-diameters so as to represent the circles inscribed in the squares 82 or hexagons 8|. The corners of the squares 82 are designated by needle point holes 83 and the ends of the horizontal and vertical bisectors or crossdiameters of the hexagons 8| and circular cutouts- 80 are indicated by needle point holes 84 and 85 respectively. The hexagonal and circular cutouts 8| and 80 are arranged in pairs side by side so that a very slight shift of the instrument brings the one into the position previously occupied by the other. Thus the heads and ends of bolts, nuts, screws and studs of various kinds are quickly and easily drawn. The various pairs of cutouts l9 and 80 are designated by fractions indicating the size thereof so that the proper pair of cutouts may be quickly selected without loss of time and used without loss of motion.

Operation The drafting instrument In may be used in a large variety of ways to assist the draftsman in drawing a majority of the lines'and laying off a majority of the dimensions or angles used in his work. Much of the operation is self-evident from the foregoing description. The base and altitude edges and I2 and the hypotenuse edges l4, l and I6 are used to draw straight lines, either horizontal or vertical or inclined to the horizontal at angles of 75, 60, or 45 when the base edge I rests on the T-square. When the altitude edge l2 rests on the T-square, the hypotenuse portions I4, l5 and I6 are used to draw lines inclined at angles of and respectively relative to the T-square or horizontal. When the first hypotenuse portion l4 rests on the T-square, the 'base edge H and altitude edge |2 are used to draw lines at angles of 75 and 15 respectively, relative to the T-square. When the second hypotenuse portion l5 rests on the T- square, the base edge H and altitude edge l2 are used to draw lines at angles of 60 and 30 relative to the T-square. When the third hypotenuse portion l6 rests on the T-square, either the base edge I or altitude edge I2 is used to draw a line at an angle of 45 to the T- square. In this manner, the drafting instrument l0 may be used to draw lines at any angle to either the horizontal or the vertical, from 15 to 90 at intervals of 15, the T-square edge serving as a base line. The three hypotenuse portions l4, l5 and 6 are of approximately equal length so as to give the maximum bearing surface on the T-square and thereby to mimimize rocking. In a similar manner, the instrument may be used to divide a circle by increments of 15 into a total of 24 divisions.

The eighth, tenth and twelfth inch scales l1, I8, l9, 2|, 22 and 23 with their needle point holes 26 enable the draftsman to perform accurate dimensioning of machine parts without recourse to additional scales. All three scales are frequently required in order to dimension a single part, for example, in gearing. Gears are commonly used having six, eight and ten diametral pitch. For the six diametral pitch gear, the addendum and dedendum' circles are approximately inch, hence the twelfth scale |9or 23 is used with its twenty-fourth inch divisions. For an eighth diametral pitch gear, the eighth inch scale or 2| is used with its sixteenth inch divisions. When dimensioning is made according to the decimal system, such as in. naval architecture and machinery, the tenth inch scale l8 or 22 is used with its twentieth inch divisions. In each case, the needle point is inserted through the proper hole 26 and a prick point'made in the drawing to guide the subsequent drafting. As it is not uncommon to have eight, ten and twelve diametral pitch gears on the same sheet of de'-.

tails, the drafting, instrument l0 can be used to dimension all three without requiring any additional scales. Furthermore, much architectural drafting and machine drawings are made to a scale of one inch equalling one foot and in such work, the twelfth inch scale l3 or 23 is used without the necessity of recourse to additional scales or to the more laborious procedure of interpolating between the 1 1; inch graduations on an ordinary scale. The use'of the needle point is much more accurate than that of a pencil point.

To lay out angles, the protractor scale 21 is employed, using the center point 30 and the line 28 or 29 for reference. A needle point is used to lay out a prick point for. the correct angle. The small protractor 32 near the corner 2|] of the instrument is employed to enable the easier lining up of the desired angle. to the center 30, and the accurate division is located on the large protractor scale 21. The use of the needle point holes 26 and 32 eliminates parallax which occurs when scales are ordinarily inscribed on draftsmans triangles, because these scales are placed on the topsurface of the triangle and its thickness creates a parallax error.

The lettering guide portion 34 at the lower lefthand corner of the instrument enables either vertical lettering or slant lettering to be quickly and easily drawn, the sides 4| and 42 giving included angles of 120 or angles of 60 to the T-square edge or base line. The pencil holes 39 or 40 used in conjunction with the cutouts 35, 36, 31 and 38 enable the heights of the letters to be accurately laid out and ruled ofi by means of a pencil inserted through the holes. The cutout 3! enables lines of 30, 60 or inclinations to be drawn in lettering, and the cutout 38 enables horizontal and vertical letter lines to be drawn.

To lay out screw threads, V-blocks, gibs, screw heads, chamfers, etc. the thread guide portion 54 is used. The cutout 55 with its 60 and 120 angles is used for the layout of drill points, bottoms of drill holes, sides of hexagons, 30 and 60 chamfers, and center drills or lathe centers. The cutout 56 is used for laying out parts having 45 or angles, such as squares, V-grooves or ridges, 45 chamfers, sectioning and the like. The cutout 51 with its 82 included angles is used for the layout of fiat head and oval head machine screws, cap screws and wood screws. The cutout 58 with its 29 included angle is used for acme screw threads, worm threads, teeth of gear racks and 14.5 pressure angles, and the like. These cutouts are also used in conjunction with the scales l1, I8 and I9 or 2|, 22 and 23 to lay out the dimensions of the threads according to the number per inch.

The bolt and screw guide portion 18 is used to draw the heads of square and hexagonal head machine screws and nuts, as explained in connection with the construction thereof. This arrangement of the inscribed circle adjacent the with the aid of acompass.

, square and hexagon to \vhich it pertains requires only a -slight shift of the instrument for its use, and the proper .set is immediatelyselected according to the designating fraction inscribed betweenthem. 1

The irregular curve cutout 13 is used, as described in lconnection with-its construction, for the drawing'of curves which are not easily drawn The arrangement of the various parts and 7 portions of the drafting instrumentlii in acom- Da'gt formwith a minimum of movement required toaccomplish the various operationsreduces the smearing of the drawing-s to .a minimum, This probl m.

Although the instrument has been described as made from transparent material, it is also contemplated that where high precision is of greater importance than transparency, the instrument may be made of a more durable material. notsubject to shrinkage. Such a material is stainless steel, and'its, employment adapts the instrument to use by machinists, carpenters and other work'- ers requiring a very durable and precise instrument. V

WhileI have shown and described my invention in.'detail it is tov be understood that the sameis to belimitedonly by the appended claim, for many changes may be madewithout departing from thespirit and scope of, my invention.

'What I claim is: V

A drafting instrument comprising a polygonal plate-like member with a reference edge .and including a iastenerfhead guide portion with a multiplicity "of pairs of circle and hexagonoutouts arranged side by side in a single path extending alongside said reference edge and increasing progressively in size from one lend ofs aid xcertain corners ofsaid hexagon cut-outs, the

needlepoint holes adjacent the corners of each hexagoncut-out forming the corners of a square ,ofsubstantially the same dimensions as the diameter of the corresponding circle cut-outof each pair of hexagon and circle cut-outs,

- OWEN D. PREMO. 7

REFERENCES, CITED The following references are of record in the file of, this patent:

UNITED sTA'rEs PATENTS Number i Name Date 11138,.016 Gilardi June 6, 1944 D. 139,083 Macht Oct. 10, 1944 434,073 Rondinella Aug. 12, .1890 462,126 Grifiiths Oct. 27, 1891 727,680 Otis May 12, 1903 1,139,229 'Requa May 11, 1915 1,433,083 Leishmann Oct. 24, 1922 1,579,137 Pecker Mar. 30, 1926 1,667,191 Chopin Apr. 24, 1928 1,704,540 Keufiel Mar. 5, 1-929 [1,751,366 Shaub Mar. 18, 193.0 1,755,024 Sanden Apr. 15, 1930 2,043,729 Bildergu June 9, 1936 2,122,732 Uyeda et al. July 5,1938 2,242,286 vBoughton May 20, 1941 2,243,579 Rodi- May 27,1941 2,247,362 Dibble July 1, 1941 FOREIGN PATENTS Number 1 Country Date 2365 Great Britain Feb. 2, 189.5 1,564 Great Britain 191 0 5,753' Great Britain Mar. 10, 1910 662,148 France Mar. 18, 1929 268,259 Italy Oct. 9, 1929 .02.29

Australia Oct. 23, 1936 Th I 1-.-... 

